1. Field of Invention
The invention relates to machines used for stringing tennis rackets and the like and particularly to those machines which incorporate structure designed to assist in the obtaining of the desired objective of a uniform tensioning of the strings.
2. Description of Prior Art
For prior art disclosures of similar types of racket stringing apparatus see U.S. Pat. Nos. 2,069,736; 2,067,563; 2,154,870; and 3,441,275. These show apparatus of a nature only generally similar to that herein shown, lacking specific features of advantages referred to in the Abstract and hereinafter further described and claimed. More particularly, the supports for holding the racket during the stringing operation are structured in a manner permitting minor but critical flexing thus affecting the resulting string tension, and uniformity of tensioning, and failed to hold the racket head frame against small but critical deflection which likewise affects the tensioning of individual strings and the string-to-string tension across the playing face of the racket. Variations of tension from string to string in rackets strung on prior art machines may vary as much as 10 to 15 pounds. In such case, the primary driving force is imparted to the ball by the tight strings with the looser strings more or less riding free. The presence of adjacent relatively tight and loose strings causes a shift in the direction of exiting of the ball from the racket; and it will be apparent that only a very small angle of error of the ball leaving the racket will produce an error of several feet as the ball reaches the opponent's back court. In tennis and similar games, optimum accuracy in ball placement is critical. Where the racket head is permitted to move or bow during stringing, strings which are placed will be subsequently relaxed if later placed strings shorten the distance across the racket head either longitudinally or transversely. Normally, the main or longitudinal strings are first placed in the racket head. If the racket head is allowed to distort during the placement of the longitudinal strings, the addition of each string reduces the tension of every string that is already in place, thus creating a variation of tension from string to string. When the cross strings are placed in the racket head, an increase in tension of the main strings will normally occur, but the difference in tension from string to string is not corrected.
Other stringing errors may be introduced by the string clamps used to anchor the string as it is tensioned within the racket head and to engage and apply the tensioning force to the string. Prior art structures have permitted minor but critical displacement of the former, and have frequently produced a crushing and damaging of the string in the case of the latter, both of which affect the tensioning and overall quality of the racket.